Generally, a floating zone (FZ) method or a CZochralski (CZ) method has frequently been used as a method of manufacturing a silicon single-crystal. The growth of a silicon single-crystal ingot by an FZ method has several problems, such as difficulty in manufacturing a large-diameter silicon wafer and considerably expensive process costs. Therefore, the growth of a silicon single-crystal ingot using the CZ method is prevalent.
With the CZ method, after polycrystalline silicon is stacked into a quartz crucible and is melted by heating a graphite heating element, a seed crystal is dipped into the resulting silicon melt to cause crystallization at the interface of the silicon melt and is then pulled while being rotated, thereby completing the growth of a single-crystal silicon ingot.
The single-crystal ingot grown by the above-described method includes a neck portion, which is connected to the seed crystal and is formed in a thin and long shape, a shoulder portion, which is grown by gradually increasing the diameter of the single-crystal ingot after a necking process, a body portion, which is grown in an axial direction while maintaining the increased diameter, and a tail portion, which is formed by gradually reducing the diameter of the single-crystal ingot that is being grown and is separated from the silicon melt.
In the case of a conventional silicon single-crystal ingot growing apparatus and a single-crystal ingot growing method using the same, because the top of a crucible is open, a single-crystal ingot may exhibit uneven distribution of heat during a growth process thereof, and in addition, a difference occurs in the cooling rate between the central portion and the peripheral portion of the cross section of the single-crystal ingot.
Due to such a temperature gradient in the radial direction of the single-crystal ingot, crystal defects formed in the center area and the peripheral area of the cross section of the single-crystal ingot have different distributions at the same position in the pulling axial direction. Therefore, it is difficult to grow the single-crystal ingot by increasing a defect-free crystal area.